In the field of automotive lighting, there have been significant efforts directed to the purpose of reducing the overall number of lighting components as well as the size of such components that are necessary for achieving a proper pattern of road illumination. It is well recognized that by improving the front end profile of an automobile, a more efficient aerodynamic performance will result. This has appeal to the automotive industry because this improvement in turn, not only leads to improved fuel efficiency for that vehicle, but also provides more of an incentive to the automobile buyer looking for a more updated design.
In a typical automobile forward lighting arrangement, there can be up to four separate sources of light, one source for each automobile side (driver, passenger) and one source for the high beam and low beam functions on each side. Additionally, there is a need for reflector assemblies for each side of the automobile. It can be appreciated that with this many sources of light, in addition to the space and complexity such design requires, there is in the case of discharge sources in particular, the added disadvantage that the color of the light from the various sources can vary to the point that there is a considerable and apparent difference between such light sources. With the use of a typical discharge lamp for such source of light, should one of the lamps need replacing at a different time than the other lamps, this distinction in color as well as intensity can be very pronounced and quite a distraction to any driver approaching from the opposite direction. Of course, one way to avoid such color and intensity distinction as occurs when one lamp is replaced would be to replace all of the lamps, however, such a solution is obviously economically impractical.
One way to avoid the problem of color and intensity variations between lamps on a single vehicle would be to provide the vehicle with a single forward lighting source. A single source of light also has the advantage that once the light source is energized, it remains on regardless of whether the driver switches between low beam and high beam operation. In a typical multiple light source arrangement, there is a need to switch between an "on" and an "off" operation of the particular lamp for each conversion between low and high beam operation. The disadvantage with this approach is that this constant switching must be accomplished in a manner that ensures that the light output will be available in essentially an instantaneous manner. Also, this approach requires a constant switching operation for the ballast circuit which is driving the light source.
Accordingly, one approach to reducing the overall size requirements for an automotive forward lighting application and to avoid the above described disadvantages of utilizing a multiple light source arrangement would be to utilize a single source of light and a light distribution arrangement utilizing optical fibers. By using this approach, the light source portion of the system can be moved to a position remote from the front end of the automobile thereby allowing that the light output can be distributed to the various positions as necessary by means of a fiber optic/light guide arrangement. An example of such an approach can be found in U.S. Pat. Nos. 4,811,172 and 4,958,263 issued to Davenport et al and assigned to the same assignee as the present invention.
It would be further advantageous of a system that utilizes a single light source if such system also minimized the number of components necessary to distribute the light output in a manner to achieve the light pattern illumination required by the Society of Automotive Engineers standards. It is known that by using optical fibers for channelling the light output to locations remote from the source that there are losses associated with the transmission of light through long lengths of fiber optic cables. Therefore, it would also be advantageous if a system using a single light source could be constructed in a manner to require as little amount or distance of fiber optic cable as possible while still achieving the benefit of the remote location of the light source.
Referring once again to the SAE standards for the pattern of road illumination for an automobile forward lighting application, the considerations that a lighting designer must keep in mind when trying to improve the system of automotive forward lighting are such that there are essentially two components of the pattern of road illumination that must be achieved. The first of these components is the high brightness or "punch" component which is defined in terms of lumens per steridian and which provides a more focussed, narrow beam of light near the center of the pattern. The second component is the "spread" light which, as the name implies, is the light which is spread on a broader pattern across the road and is measured in terms of total lumen output of the forward lighting system.
Presently, to achieve this pattern of road illumination, a mirror and lens element is provided at each of the light sources. This mirror and lens element typically contains a complex array of reflective surfaces or refractive elements that all interact in a manner to sum the individual light components into a composite light output which includes both punch and spread portions of the illumination pattern. The light outputs from each of the separate light source/lens arrangements can then be superimposed in a manner to achieve an overall pattern of road illumination in compliance with the SAE standards.
It would be advantageous and extremely cost effective if a lighting arrangement were developed which would avoid the need for having multiple lens elements of such a complex nature. Furthermore, if such a new automotive forward lighting arrangement were developed, it would be advantageous if such lighting arrangement could more precisely achieve both the punch and spread components in a manner that would avoid having the spread portion extend too far upward and into the path which could distract drivers in the opposite direction.
A further advantage to the use of a single source of light disposed in a location remote from the point at which the light is output is that because of environmental concerns over the harm that may be caused by materials used in automotive heating and cooling systems, a less efficient and more bulky material may be used in place of materials considered harmful to the environment. Accordingly, by removing the light source from the front of the vehicle thereby reducing the amount of space needed for the lighting operation in this front area, automotive designers can more effectively put this space to use for other critical purposes. Additionally, by disposing the single light source in a position remote from the front end point of delivery, the light source can be made more collision resistant; that is, in a minor collision there may be no damage to the light source if it is disposed in a more protected area.